Some more removals of dart:utf.

sdk/lib/_internal/compiler/implementation/source_file_provider.dart

Index: sdk/lib/_internal/compiler/implementation/source_file_provider.dart
diff --git a/sdk/lib/_internal/compiler/implementation/source_file_provider.dart b/sdk/lib/_internal/compiler/implementation/source_file_provider.dart
index 3188a3e159ba5dcdf1b87956b004b170a84a4a32..ca48fda6604213e825de9370ec84ce16a4187aff 100644
--- a/sdk/lib/_internal/compiler/implementation/source_file_provider.dart
+++ b/sdk/lib/_internal/compiler/implementation/source_file_provider.dart
@@ -5,8 +5,8 @@
 library source_file_provider;
 
 import 'dart:async';
+import 'dart:convert';
 import 'dart:io';
-import 'dart:utf';
 
 import '../compiler.dart' as api show Diagnostic;
 import 'dart2js.dart' show AbortLeg;
@@ -21,7 +21,7 @@ String readAll(String filename) {
   var buffer = new List<int>(length);
   var bytes = file.readIntoSync(buffer, 0, length);
   file.closeSync();
-  return new String.fromCharCodes(new Utf8Decoder(buffer).decodeRest());
+  return UTF8.decode(buffer);
 }
 
 class SourceFileProvider {